Oscillation generator for electrical musical instruments



u y 1, 1941- N. LANGER ,247,728

OSCILLATION GENERATOR FOR ELECTRICAL MUSICKL INSTRUMENTS Filed Feb. 13,1959 ZSheets-Sheefl 2/ I T P 5/ 0H v/z INVENTOR I July 1, 1941. N.LANGER OSCILLATION GENERATOR FOR ELECTRICAL MUSICAL INSTRUMENTS 2Sheets-Sheet 2 Filed Feb. 13, 1939 INVENTOR 1 4424/) law Patented July1, 1941 QSCILLATIDN GENERATOR FOR ELEC- TRICAL MUSICAL INSTRUMENTSNicholas Longer, New York, N. Y., assignor oi sixty-six and two thirds'per cent to John Halmagyi, New York, FL Y.

application February 13, 1939, Serial N 256,101

23 Claims.

The present invention relates to the art of producing electricaloscillations, and, more particularly, to an oscillation generator forthe production of electrical oscillations of musical irequency in whicha condenser is periodically charged and discharged through resistancesand glow-discharge tubes. I

It is an object of the present invention to provide an oscillationgenerator of novel and improved character in which alternate electricaldischarges take place in a plurality of glow-dislowing description takenin conjunction with the accompanying drawings, in which:

Fig. 1 illustrates a novel circuit embodying the present invention andemploying a pair of glowcharge tubes and cooperate in generatingelectrlcal oscillations of a complex and desirable wave form.

It isanother object of the invention to provide an oscillation generatorof the glow-diseharge tube type which is capable of producing electricaloscillations having a substantially constant frequency and includingvery strong harmonics of a desirable character.

It is a further object of the invention to provide an oscillationgenerator involving a pair of glow-discharge tubes which are alternatelyenerglzed through a system of resistors and at least one condenser andcapable of producing an oscillation of musical frequency in some of theparts of the circuit and an oscillation of double of such frequency inother parts of the circuit.

Still another object of the invention is to provide a twinglow-discharge tube oscillator including a pair of glow-discharge tubesthrough which alternate discharges take place when combined in asuitable manner with a condenser and with a pair of resistances, withoutrequiring any inductances in the circuit.

The invention also contemplates a system of oscillation generators eachbeing capable of producing an electrical oscillation of musicalfrequency and its octave combined in such a manner that oscillatoryenergy is transferred from each oscillator of the system to a subsequentoscillator thereby to establish preferred and constant frequencyrelationships throughout the system.

' It is also within contemplation of the invention to provide anelectrical musical instrument including a plurality of twinglow-discharge tube oscillation generators, each comprising a palrofalternately excited glow-discharge tubes and produclng electricaloscillations of musical frequency having the interval of one octavetherebetween and having interrelations between subsequent oscillators ofthe series to positively maintain said octave interval constant.

Other and further objects and advantages of .the invention will becomeapparent from the foldischarge tubes in cooperating relation ior theproduction of electrical oscillations;

Fig. 2 depicts a similar circuit for the produc tion of electricaloscillations of musical frequency and includes a plurality of couplingmembers for withdrawing oscillations of dlfierent frequency andwave-form from the various parts of the circuit; and

Fig. 3 shows a system of oscillation generators of the type illustratedin Figs. 1 and 2 for the purpose of producing a plurality ofoscillations of musical frequency having a stable and positivelyconstant frequency interval therebet-ween.

Broadly stated, according to the principles of the present invention,the foregoing objects are attained by electrically associating two ormore glow-discharge tubes into a circuit in such a manner that theoscillatory current set up by one of them influences the-production bythe others, and vice versa. Thus, two glow-discharge tubes may beelectrically associated with each other so that the voltage on one ofthe tubes depends on the momentary condition of the other, whether it isconducting current at that particular moment contemplated, or not. Ihave discovered that when such interrelations are established betweenglow-discharge tubes, 2. number of individual oscillations will be setup in different parts of the circuit 'ilfhese oscillations may havefrequency and phase differences and such frequency and phase difierencesare automatically maintained constant indefinitely even though theelectromotive force, the capacities and the resistances in the circuit,or the characteristics of the glowdischarge tubes may vary considerably.

More particularly, 1 have made the discovery that a pair ofglow-discharge tubes may be combined with a source of direct currentpotential, with a. pair of resistances and with a single condenser toproduce electrical oscillations of great frequency constancy andamplitude and containing very strong harmonics. Moreover, I have foundthat in circuits of the character described, the harmonic content of theoscillations greatly varies in the various parts of the circuitsaccording to whether the part of the circuit contemplated is in commonfor both glow-discharge tubes, ornot. Thus, some parts of the circuitcarry strong currents having twice the frequency of the oscillatorycurrents set up in other parts of the circuit.

This interesting and important property of my novel glow-discharge tubeoscillators may be put to use with great advantage in the construction oelectrical musical instruments in that a pluty of oscillations ofdifferent frequency and of ifierent wave-form of harmonic content may bedclived from a single oscillation generator. As a iurther development ofthis basic inventive cona pliuality of such oscillation generators areprovi" ed, each producing oscillations which are separated from eachother by a predetermined interval, such as an octave. In addition tothis oscillation, each oscillation generator also produces anoscillation oi the same frequency as that of the next oscillationgenerator and this oscillation may be introduced into the next genc' torto exert a strong l cking andstabilizing influence thereon which cannotbe destroyed or interrupted even very great changes in the controllingfactors oi the individual glow-discharge tube oscillators, such as inthe capacities, resistances, critical voltages of the tubes, and thelike. Thus, a system of glow-discharge tubes is provided which isself-stabilizing in that the individual oscillation generators mutuallyassist each otherin maintaining constant frequency intervalstherebetween. Thus, not only a large number of constant frequencyoscillations may be produced but at the same time a large number or"different wave-forms of the various frequencies may be derived from thevarious portions of the system, as it will be explained more fullyhereinafter.

Referring now more particularly to Fig. 1 of the drawings, a fundamentalcircuit embodying the principles of my invention is illustrated which inthe following will be referred to as a twin glow-discharge tubeoscillator or simply twin oscillator. Essentially, a pair ofglow-discharge tubes I and 2 is provided, each being connected in serieswith a resistance I I and I2, respectively. Both tube I with its seriesresistance I I and tube 2 with its series resistance I2 are connectedacross a suitable source of direct current 3| having a voltage in excessof the breakdown voltage of the tubes, A condenser 2| is connectedbetween the common terminal of tube I and resistance II and the commonterminal of tube 2 and resistance I2.

As to the electrical constants of the circuit, wide variations arepossible. Preferably, the tubes are of a similar type although thisconsideration is by no means critical as tubes of widely varyingbreak-down and extinction voltages can be employed in the twinoscillator circuit. Generally speaking, the resistances and thecondenser have similar values as employed in the single glow-dischargetube oscillation generators such as are described in my U, S. Patent No.1,832,402, granted November 17, 1931. To give a practical example, ifcondenser 2I is about 0.001 microfarad, resistances II and I2 are about2 megohms each, and the voltage of direct current source 3| is about 100volts, oscillations of musical frequency will be set up in the circuit.

The study of the oscillatory processes in a circuit of this type isgreatly facilitated when the capacity of condenser 2| is made verylarge, such as several microfarads. In this case, the oscillations setup in the circuit'become extremely slow, only one oscillation or currentimpulse in several seconds, so that the flow of current in the diiferentparts of the circuit and through the individual glow-discharge tubes maybe studied at leisure. 1

When the circuit illustrated in Fig, 1 is completed, it will be foundthat both tubes I and 2 will be periodically lit and extinguished atpredetermined constant time intervals. It will be also observed that thetwo tubes are never lit at the same time but when tube I is lit, tube 2is always extinguished, and vice versa. Thus, two electricalOscillations are produced in the circuit, said oscillations having thesame frequency but having a constant phase diiference. The phasediiference varies with the proportion of the resistances II and I2 andis approximately degrees when the two resistances are equal, Of course,instead of employing two fixed resistances as indicated in Fig. 1, it isalso possible to employ two variable resistances of appropriate value,or a single resistance having an intermediate tap which is connected tothe lower terminal of the battery, or, finally, a single resistancehaving a sliding contact thereon whereby the phase difference betweenthe two twin oscillations may be readily adjusted to a predetermined andpreferred value. Of course, when it is desired to produce oscillationsof musical frequency, such as are required in the construction andoperation of electrical musical instruments, capacities of about 0.0001to about 0.01 microfarad are employed in the circuit and of particularinterest is the case when the resistances I I and I2 are substantiallyequal.

The reasons for thi type of operation of the circuit are not completelyclear and I do not wish to attempt a theoretical explanation of suchoperation, although an approximate idea may be formed as to the reasonwhy the two glowdischarge tubes will never be lit at the same time. Itmay be assumed that in all cases there is a slight difference betweenthe breakdown voltage of tubes I and 2. Assuming that tube I has thelower break-down voltage, a. momentary discharge will take place throughthis tube, and through resistance II which is in series therewith. Assoon, however, as current flows through the branch of the circuitcontaining tube I and resistance II, a difference of potential will becaused between the common terminal of tube I and resistance II and thecommon terminal of tube 2 and resistance I2, between the which condenser2I is connected. This difference of potential will cause charging of thecondenser and this charging current will reduce the potential availablefor tube I still further so much that it will fall below the extinctionvoltage thereof, As soon, however, as tube' I is extinguished, condenser2| will add its voltage to that of the voltage applied to tube 2, whichnow will break down and will discharge condenser 2|. This discharge willlower the potential of common terminal B below that of A, so thatcondenser 2i will be again charged in the opposite direction thanbefore. This charge and discharge of condenser 2-I and the alternatedischarges through tubes I and 2 will be periodically repeatedindefinitely sistance oi resistances II and I2, same as in the case ofthe simple glow-discharge tube oscillator. Obviously, the number ofdischarges during a predetermined time interval must be exactly the samethrough tubes I and 2, there being, how-- ever, always a constant phasedifierence, for example, 180 degrees, between these oscillatorycurrents. In the part of the circuit which is in common for both tubes,such as leads C and D of the common source of current, both oscillatorycurrents will be present. This resultant current will be extremely richin harmonics, as it will contain the fundamental and the harmonics ofboth oscillations produced in the individual branches of the circuit.Particularly the second harmonic, or the octave, of the oscillationsproduced in the individual branches of the circuit will be very stronglyexpressed in the common branch of the circuit. Those skilled in the artwill readily appreciate that this is of very great practical importanceas both a fundamental frequency and its octave may be simultaneouslyderived from my novel twin glow-discharge tube oscillator. Thus, twooscillations may be obtained which always have the constant interval ofan octave between their respective frequencies, a circumstance which isof great interest and value in the construction and operation ofelectrical musical instruments capable of producing musical chords.

Of course, oscillatory currents of different character and frequencywill flow in the different portions of the oscillation generatorillustrated in Fig. 1. Thus, as it has been set forth in the foregoing,in leads E and F, in which only current of a single glow-discharge tubeflows, complex oscillations of identical frequency will flow having aconstant phase difference and a fairly strong amplitude. In resistors Iiand I2 currents of the same frequency will flow as in leads E and F,respectively, however, they will have a smaller amplitude than theformer and will be somewhat poorer in harmonics in view of the fact thatnot all of the current passing in leads E and F will pass throughresistances II and I2 but some of it will flow over condenser 2|. Inleads C and D very strong oscillations will be present as in these leadsthe currents flowing through both tubes will be superimposed upon eachother. In other words, in leads and D a very complex oscillatory currentwill be present which generally speaking contains the octave of thefundamental and of all of the harmonies individually present in leads Eand F. In the branch of the circuit between points A musical tone whenconverted into sound vibrations by means of a suitable translatingdevice.

Fig. 2 depicts a circuit similar to the one illustrated in Fig. 1 withthe difference, however, that coupling means are provided in the variousportions of the circuit to selectively withdraw oscillatory energy ofdifferent frequency, or of different wave-form, or both. Although inthis modified embodiment transformers have been shown as coupling means,obviously coupling means of various type. such as condensers, chokes,resistances, and combinations thereof may be employed for the selectivewithdrawal of oscillatory energy with equal or similar results. In otherwords, the coupling means may be of an inductive, capacitive, orgalvanic character and preferably provide a coupling loose enough toprevent the reflection of energy from the exerator proper, as suchreflection might interfere with the stability of the oscillationsproduced or might introduce undesirable harmonics into the oscillationgenerator.

In Fig. 2 essentially the same elements are employed as in the circuitof Fig. 1. Thus, a glowdischarge tube 3 is connected in series with aresistance i3 and a second glow-discharge tube 4 is connected with aresistance It. Likewise, same as in Fig. l, a condenser 22 is connecmdacross the common terminal of tube I and resistance l3 and the commonterminal of tube 4 and resistance 14. Direct current voltage is appliedto both tubes Stand A and to their respective series resistances l3 andit from a suitable source of direct current 32. As it will be readilyobserved from Fig. 2, the tubes and their resistances are not directlyconnected to the source of current but through the primary windings of aplurality of transformers iii, d2, d3, M and 43. Thus, primary windingan of transformer M is interposed in series with the upper lead of tube3, primary winding 52 of transformer 42 is interposed in series with theupper lead of tube a, primary winding 53 of transformer 43 is connestedin series with the lower end of resistance I3 and primary winding 54 oftransformer N is connected in series with the lower end of resistance H.In addition to this, primary winding 58 of transformer 46 is connecteddirectly in series with the source of current 32 in the common or mainbranch of the circuit in which current from both tubes is flowing, andprimary winding 55 of transformer 45 is connected in series withcondenser 22. Thus, from secondary windings 6i, 6!, 53, 54, and 56 ofthe transformers, six oscillations of different character vmay besimultaneously derived. The oscillations derived from secondary windingsSI and 62 are identical in frequency and in their harmonic content butthey are displaced in phase by a constant amount. Likewise, secondarywindings and 66 provide oscillatory currents of the same frequency as GIand 62 and also have a constant phase difference therebetween but theyare considerably poorer in the higherharmonics. Secondary winding 66supplies oscillatory energy from the main branch of the circuit, havingdouble the frequency of the oscillations derived from the secondarywindings and having strong harmonics and a great amplitude, whereassecondary winding 65 delivers substantially sinusoidal oscillations ofthe same frequency as secondaries Bl or 62, but relatively poor inharmonies. Preferably, condenser. 22 is of an adjustable capacity inorder to adjust the frequency of the oscillations produced andresistances l3 and I4 are also of an adjustable character in order toadjust the phase difference between the 60 oscillations in the variousparts of the circuit to a predetermined and preferred value. As it willbe readily understood by those skilled in the art, the circuit of thetype described in connection with Fig. 2 has great value for theproduction of musical sounds in eiectricalmusical instruments as anumber of oscillations of different character and of constant frequencyintervals may be generated by a single circuit, such as those imitatingthe musical qualities of the diapason, flute, string and reed stops of apipe organ. Moreover, sounds of a predetermined frequency and the octaveof such sounds may be simultaneously produced, any deviations from thetrue relative tuning being positively prevented. Of course, in-

ternal or load circuit into the oscillation gen- 7 stead of emp n 6output a sfo ers in the various parts of the circuit, transformers orsimilar coupling means more or less in number than six may be employedaccording to other practical considerations.

Very naturally, in an electrical musical instrument, a large number ofoscillation generators is required, generally speaking one oscillationgenerator for each note of the musical range of the instrument, such as88, or more, in number. This is not objectionable, in view of the factthat the glow-discharge tubes, of which two are r quired for eachgenerator, and also the other elements of the generator, are small indimensions and are low in cost. It very desirable, however, to posicmclyassure that constant freicy intervals are maintained between thenoivldual generators. This be accomplis ed transferring small amounts ofoscillatory "gy from one oscillation generator to the others. My twinglow-discharge tube oscillator is particularly adaptable for carryingthis concept into practice in view of the fact that from eachoscillation generator a fundamental frequency and its octave can bereadily derived simultaneously. For this reason, it is preferred toestablish such inter-relation between a series or system of twinoscillators which are tuned to subsequent octaves, for reasons whichwill appear more fully hereinafter.

A circuit of such character is depicted in Fig. 3. Although only 3 twinoscillators are illustrated tuned one octave apart from each other,obviously, any suitable number of similar oscillators may be employed,such as '7 or 8, in order to provide the successive octaves of a note ofthe tempered scale for the full musical range. As it will be .readilyunderstood from the drawings, each of the three twin oscillators I, II,and III is substantially similar to the ones depicted in Figs. 1 and 2.Thus, oscillation generator I comprises a pair of glow-discharge tubes 5and 5, which are connected in series with resistances I 5 and I6,respectively, and a variable condenser 23 is connected between thecommon terminal of tube 5 and resistance and the common terminal of tube6 and resistance 16. Likewise, twin oscillator II essentially comprisesglow-discharge tubes 7 and 8 connected in series with resistances l1 and18, respectively, and having a variable condenser 24 connected betweenthe common terminal of tube 1 and resistance I1 and the common terminalof tube 8 and resistance l8. Twin oscillator III comprisesglow-discharge tubes 9 and i0, connected in series with resistances l9and 20, respectively, and a variable condenser 25 is connected betweenthe common terminal of tube 8 and resistance I9 and the common terminalof tube 10 and resistance 20. Direct current potential is supplied toall three twin oscillators from a source 33. Oscillator I is suppliedwith current through the primary winding 8| of a transformer II, the twoends of said winding being connected to tubes 5 and 6, respectively,while a center tap of primary winding 8| being connected to the upperterminal of source 33 through the primary winding 51 of an outputtransformer 41. Oscillator II is supplied with current through thesecondary winding SI of transformer H having one of its ends connectedto tube 1 and having its other end connected to primary winding 82 of atransformer 12, the other end of said primary winding 82 being con'-nected through a choke coil [M to tube 8. The center tap of the primarywinding 82 of transformer ":2 is connected to the upper terminal ofsource 33 through the primary winding of output transformer 48.Oscillator III is supplied with current through the secondary winding 82of transformer 12' having one of its ends connected to tube 9 and havingits other end connected to primary winding 88 of transformer 13, theother end of said primary winding 83 connected through a choke coil 102to tube 8. The center tap of the primary winding 33 of transformer 13 isconnected to the upper terminal of source 33 through the primary winding59 of output transformer 49. Secondary winding 33 of transformer I!provided for connection to one of the tubes of the subsequent twinoscillator and to its transformer corresponding to similar elements oftwin oscillator III. In addition to output transformers ii, #8, 48,similar output transformers fill, H2 andlES are provided having theirprimary. windings I21, I22 and 23 in series with condensers 23, 2!, and25, respectively.

From the preceding description, operation of the circuit illustrated inFig. 3 will be readily understood by those skilled in the art. Theelectrical constants of twin oscillators I, II and III are so selectedand condensers 23, 24 and 25 are so adjusted that if the fundamentalfrequency produced by twin oscillator I is denoted by 1, twin oscillatorII produces a fundamental frequency of 2), and twin oscillator IIIproduces a fundamento] frequency of 4 Of course, any suitable number ofsuch twin oscillators may be connected in the same manner, subsequentoscillators of the series having fundamental frequencies of 8f, 16/.etc. Generally speaking, it is not necessary to provide variableresistors, but resistances l5 and i6 may be fixed resistors of equalvalue, same as resistances IT and l8, l9 and 20.

ferring now more particularly to twin oscillator I, it will be readilyobserved that this oscillator is substantially identical with thecircuit shown in Fig, 1. Therefore, oscillations of constant frequencieswill be produced in the various portions of the circuit. In accordancewith the principles governing the production of such oscillationsexplained in the foregoing, the lowest of the frequencies produced willbe I, and such oscillation will be present, for example, in the windingsof output transformer ill, in the pertions of the circuit directly inseries with tube 5 or with tube 6. However, as the primary of push-pulltransformer H is in series with both tubes 5 and 6, oscillations havinga frequency of 2} will be produced therein and an electro-motive forceof such double frequency will be present in the secondary winding SI ofsuch transformer. The conditions will be similar in twin oscillator IIin which electrical oscillations will be set up having afundamentalfrequency of 2f. Therefore, in series with tube 1 alone, the frequencywill be 2f, that is the same as the electro-motive force acrosssecondary winding 9| which is connected in series with tube 1. In casethe polarity of secondary winding 8| is correctly selected with respectto the phase of the oscillations through tube 1, these oscillations ofidentical frequency will be in step with each other so that theoscillations of twin oscillator I will exert an extremely strongstabilizing influence upon the frequency of the oscillations produced bytwin oscillator II. Experiments have demonstrated that this stabilizinginfluence is so strong that even very great and intentional changes inthe electrical constants of twin oscillator II are incapable of pullingit apart and the exact frequency interval of one octave will bemaintained indefinitely,

, a strong stabilizing influence thereon.

no means critical, the choke coil may be omitted without detrimentaleffects.

The same remarks apply to twin oscillators II and III which areconnected with each other in the same manner as oscillators I and II. Inview of the fact that the primary winding 82 of push-pull transformer 12is connected in series with both tubes 1 and 8, oscillations of afrequency of 4f will be set up in secondary Winding 92 which isconnected in series with tube 9 of twin oscillator III of which thefundamental frequency equals 4). Thus, the double frequency 4] ofoscillator II will be impressed upon the portion of oscillator III inwhich a current of the frequency of 4,1 is flowing and will exert Itwill be readily understood that the frequency of oscillator III cannotbe changed individually due to the great stabilizing influence exertedthereon. Such change would be possible only in the event that thefrequency of oscillator II is changed first. This latter frequency,however, is incapable of individual change except when the frequency ofoscillator I is first changed. Therefore, the system will automaticallyand. positively maintain its respective frequency intervals and evenintentional changes in the frequency cannot be obtained unless bychanging the frequency of oscillator I upon which the operatingfrequencies of all subsequent frequencies are based.

Secondary winding 93 of push-pull transformer 13 has an oscillationpresent therein having. a frequency of Si, which may be transferred to asubsequent twin oscillator IV (not shown) of similar character and tunedto a fundamental frequency of 8f, as those skilled in the art willreadily understand.

As to the withdrawal of the oscillations for example for the purpose ofan electrical musical instrument, this is accomplished by means ofoutput transformers or by means of similar coupling members. As a matterof fact, any desired number of output transformers may be provided inthe various parts of the several circuits, the most importantpossibilities having been indi cated in Fig. 2. Thus, in Fig. 3, outputtransformers Ill, H2 and H3 having secondary windings l3l, I32 and I33will produce oscillations of respective fundamental frequencies of f,2f, and 4f of a substantially sinusoidal character.

In contrast to this, output transformers 41, 48 I obtained havingdifferent harmonic content andv thus being capable of producing soundsof different tone color corresponding to the various stops of the organ.Of course,'the various oscillations derived from the various portions ofthe circuit may be further subjected to modifications of the harmoniccontent to obtain additional tone colors, as this is, for example,described,

more fully in my U. S. Patent No. 1,993,890, granted March 12, 1935.

Of course, the interval between the subsequent twin oscillators of theseries is notrestricted to an octave, but other suitable. intervals suchas fifth, sixth, etc., may be employed with equal or-similar results.However, in view of the fact that in the tempered scale, now almostexclusively employed in keyboard instruments of constant tuning, onlythe octaves are in a rational proportion of frequencies, it is preferredto employ the octave interval. Likewise, it is to be observed that inorder to obtain all ofthe notes of the musical range, it is necessary toprovide a series or system of twin oscillators, similar to the oneillustrated in Fig. 3, for each note of the tempered scale. Thus, aseries of oscillators Ic, 110, 1110, We, Vc, etc., is to be provided forthe subsequent octaves of the note c, a similar series of oscillatorsIcii, 1101i, 11103, We, Vet, etc. is to be provided for the note ct, anda similar series Id, Rd, 11111, IVd, Vd, etc. is to be provided for thenote d, and so forth, throughout the 12 notes of the tempered scale. Ina system of the described character, the problem of maintaining 88 or 90individual oscillators in constant frequency intervals is reduced to theproblem of maintaining the twelve lowest oscillators constant which is arelatively simple problem and may be accomplished in various wayssuch asfor example by means of the frequencystabilizing system disclosed in myU. S. Patent No. 2,044,360 granted to me on June 16, 1936. In the eventthat the production of a tremolo efiect is desired, in other wordsslight periodic changes of the frequencies produced, this canbeaccomplished by impressing a slow modulating oscillation having afrequency-of 8 to 12 oscillations per second and produced, for example,by means of a separate glow-discharge tube oscillator, as this is fullydisclosed inmy U. S. Patent No. 2,040,439, granted May 12, 1936.

It will be noted that the circuits embodying the principles of thepresent invention provide important advantages heretofore difficult orimpossible to obtain. Thus, first of all, a new and highly efiicientoscillator of remarkably constant frequency is provided which is verysimple and inexpensive in construction, .small in dimen-' sions. verymoderate in its energy requirements, and is capable of producingoscillations of a very great frequency range extending from oneoscillation in several minutes to oscillations These oscillations widelydifferent character, tone color, and frequency, simultaneously. Theoscillations so produced have also great possibilities in time delaycircuits wherein a very substantial, readily and accurately controlledtime delay or very slow and equally spaced current impulses are requiredfor time measuring, and the like. Moreover, as each discharge throughthe glow-discharge tubes is accompanied with light emission, it ispossible to utilize such periodical emission of light impulses forvarious purposes, such as flashing light impulses for various purposes,such as flashing light and danger signals, advertising signs,annunciator systems, and the like.

Although the present invention has been described in connection with afew preferred embodiments thereof, variations and modifications may beresorted to by thoseskilled in the art without departing from theprinciples of the.

present invention. Thus, the circuit depicted no it in Fig. 3 is merelyillustrative of the inventive concept of transferring energy from onetwin oscillator to a subsequent one of a series in order to maintainfixed frequency relationships therebetween. It will be readilyappreciated that such transfer of stabilizing energy may be accomplishedin many other ways, by means of coupling means of a different character,and the amount of such energy may be controlled, if desired, by means ofadjustable coupling means, potentiometers, variocouplers, variablecapacities, and the like. 1 consider all of these variations andmodifications as within the true spirit and scope of the presentinvention as disclosed in the foregoing description and defined by theappended claims.

i. An oscillation generator comprising in com bination a pair ofglow-discharge tubes, each of said tubes having only two electrodes, aresistance con ected in series with each said tubes, a semi er connectedbetween the common points said tubes and resistances, and a source ofdirect current constant potential connected across both of said tubesand resistances.

2. An oscillation gelier tor comprising in combination a pair ofglcw-dmharge tubes, each of said tubes having only two electrodes, 8.resistance connected series with each of said tues, a condenserconnected between the common points of said tubes and resistai'ices, anda source of direct current of constant potential having a voltage inexcess of the break-down voltage of said tubes connected across both ofsaid tubes and resistances whereby oscillations of predeterminedfrequency will be produced.

3. An oscillation generator comprising in combination a pair ofglow-discharge tubes, each of said tubes having only two electrodes, aresistance connected. in series with each of said tubes, a condenserconnected between the two leads connecting said tubes to theirrespective resistances, and a source of direct current of constantpotential for supplying electrical energy to both or" tubes throughtheir respective resistances.

l. An oscillation generator comprising in combination a pair ofglow-discharge tubes, each having only two electrodes, having one oftheir electrodes connected to each other, a condenser connecting theother two electrodes of said tubes, 2, pair of resistances having one oftheir ends connected to the two of said condenser respectively andhaving their th r ends connected to each other, and means for applyingdirect current of constant potential to the leads connecting said twotubes and said two resistances with each other.

5. An oscillation generator comprising in combination a pair orglow-discharge tubes, each of said tubes having only two electrodes, aresistance connected in series with each of said tubes, a condenserconnected between the common points of said tubes and resistances, and asource of direct current of constant potential connected across both ofsaid tubes and resistances wherebyoscillations of difi'erent frequencyand of different harmonic content will be produced in the differentportions of said circuit, and means for withdrawing at least one of saidoscillations of difierent frequency.

6. An oscillation generator comprising in comblnation an electricalcircuit having a main portion and two branch portions, said branchportions being connected in series with said main portion, a source ofdirect current of constant potential in said main portion. aglow-discharge tube having only two electrodes and a series resistancein each of said branch portions, a condenser connected between the twointermediate leads of said branch portions conmcting said tubes withtheir respective resistances whereby electrical oscillations ofpredetermined frequency and of constant phase difference will be set upin said branch portions and oscillations of double of such frequencywill be set up in said main portion, and means for selectivelywithdrawing said oscillations.

'7. An oscillation generator comprising in combination an electricalcircuit having a main portion and two branch portions, said branch pertions being connected in series with said main portion, a source ofdirect current of constant potential having an adjustable voltage insaid main portion, a glow-discharge tube having only two electrodes anda variable series resistance in each of said branch portions, a variablecondenser connected between the two intermediate leads of said branchportions connecting said tubes with their respective resistances wheielectrical oscillations of predetermined and of constant phasedifference will ,in said branch portions and oscillations oi dot:-

ble of such frequency will be set up in said main portion ofsaid,circuit, the phase relationship of said oscillations in said branchportions being varied when the relative values of said resistances arevaried, and coupling means in said main and branch, portions of thecircuit for selectively withdrawing oscillations of different frequency,phase relationship and harmonic content therefrom.

8. An oscillation generator comprising in combination an electricalcircuit having a main por tion and two branch portions, said branchportions being connected across said main portion, a source of directcurrent in said main portion, a glow-discharge tube and a seriesresistance in. each of said branch portions, a condenser connectedbetween the intermediate leads 0:. said branch portions connecting saidtubes with their respective resistances, coupling means in said branchportions to withdraw oscillations of predetermined frequency and ofsubstantial harmonic content, coupling means in the condenser branch or"the circuit for withdrawing oscillations of low harmonic content and ofthe same frequency, and coupling means in said main portion of thecircuit for withdrawing csciilati us of substantial harmonic content andof double frequency.

9. An oscillation generator comprising in com bination an electricalcircuit having a main portion and two branch portions, said branchportions being connected across said main port-ion, a source of directcurrent in said main portion, a glow-discharge tube and a seriesresistance in each of said branch portions, a condenser connectedbetween the intermediate leads of said branch-portions connecting saidtubes with their respective resistances, coupling transformers in saidbranch portions to withdraw oscillations of predetermined frequency andof substantial harmonic content,-a coupling transformer in the condenserbranch of the circuit for withdrawing oscillations of low harmoniccontent and of the same frequency, a. coupling transformer in said mainportion of the circuit for withdrawing osc llations of substantialharmonic content and of double frequency, and means for adjusting saidfrequencies.

10. In an electrical musical instrument, the combination comprising apair of oscillation generators tuned to frequencies in a simplenumerical proportion to each other; each of said generatorsincluding apair of glow-discharge tubes having only two electrodes, a resistanceconnected in series with each of said tubes, and a condenser connectedbetween the leads connecting said tubes with their respectiveresistances; a source of direct current of constant potential in commonfor both generators, and coupling means for transferring oscillatoryenergy from 'one of said generators to the other to stabilize thefrequency relationship of said generators.

11. In an electrical musical instrument, the combination comprising aplurality of oscillation generators tuned to frequencies in simplenumerical proportion to each other; each of saidgenerators including apair of glow-discharge tubes having only two electrodes, a resistanceconnected in series with each of said tubes, and a condenser connectedbetween the leads connecting said tubes with their respectiveresistances; a source of direct current of constant potential in commonfor all of said generators; and coupling means for impressingoscillatory energy from each generator upon the others to stabilize thefrequency relationships of said generators.

12. In an electrical musical instrument, the combination comprising aplurality of oscillation generators tuned to frequencies in simplenumerical proportion to each other; each of said generators including apair of glow-discharge tubes having only two electrodes, aresistanceconnected in series with each of said tubes, and a condenserconnectedbetween the leads connecting said tubes with'their respectiveresistances; a source of direct current of constant potential in commonfor all of said generators; coupling means for impressing oscillatoryenergy from each generator upon the others to stabilize the frequencyrelationships thereof; and means for withdrawing oscillatory energy ofstabilized frequency from each of said generators.

13. In an electrical musical' instrument, the combination comprising aplurality of oscillation generators tuned to successive octaves of anote of the tempered scale; each of ,said generators including a pair ofglow-discharge tubes having only two electrodes,- a resistance connectedin series with each of said tubes, and a condenser connected between theleads connecting said tubes with their respective resistances; a sourceconnected between the leads connecting said tubes with their respectiveresistances; a source of directcurrent of constant potential forsupplying energy to all of said generators whereby each of saidgenerators will 'produce a fundamental oscillation of predeterminedfrequency and its octave; coupling means for impressing oscillations ofoctave frequency from each generator upon the oscillations offundamental frequency of the next higher generator to stabilize thefrequencythereof; and means for withdrawing oscillatory energy ofstabilized frequency from each of said generators.

15. In an electrical musical instrument, the combination comprising aseries of oscillation generators tuned to successive octaves of a noteof the tempered scale; each of said generators having a main portion andtwo branch portions, said branch portions being connected across saidmain portion, a source of direct current in-said main portion, aglow-discharge tube and a series resistance in each of said branchportions, and

a condenser connected between the intermediate leads of said branchportions connecting said tubes with their respective resistance;coupling means for transferring oscillatory energy from the main portionof each generator onto the branch portion of the subsequent generatorfor stabilizing the frequency relationship thereof; and means forwithdrawing oscillations of stabilized relative frequencies from each ofsaid generators.

16. In an electrical musical instrument, the combination comprising aseries of oscillation generators tuned to successive notes of thetempered scale along a plurality of octaves; each of said generatorshaving a main portion and two branch portions, said branch portionsbeing connected across said main portion, a source of direct current insaid main portion, a glowdischarge tube and a series resistance in eachof said branch portions, and a condenser connected between theintermediate leads of said branch portions connecting said tubes withtheir respective resistances; coupling means for transferringoscillatory energy from the main portion of each generator onto thebranch portion of another generator tuned to a note of the tempered'scale having the same name to stabilize the frequency relationshipbetween the successive octaves of the same note; and means forwithdrawing oscillations of musical frequency from each of saidgenerators.

17. An optical signal comprising in combination a pair of glow-dischargetubes, each of said tubes having only two electrodes, a resistanceconnected in series with each of said tubes, at

' condenser connected between the two leads connecting said tubes totheir respective resistances,

and a source of direct current of constant potential for supplyingelectrical energy to both of said tubes through their respectiveresistances whereby said tubes will alternately emit light atpredetermined time intervals.

18. A flashing light signal comprisingin combination a pair ofglow-discharge tubes, each of said tubes having only two electrodes, aresistance connected in series with each of said tubes,

a condenser connected between the two leads connecting said tubes totheir respective resistances, a source of direct current of constantpotential for supplying electrical energy to both of said tubes throughtheir respective resistances whereby electrical oscillations will beproduced and said tubes will alternately emit light at predeterminedtime intervals, and means for adjusting the frequency of saidoscillations for varying said time intervals.

19. An oscillation generator comprising in combination a pair ofglow-discharge tubes, each of said tubes having only two electrodes, aresistence connected in series with each of said tubes, c condenserconnected between the two leads connecting said tubes to theirrespective resistcnces, a source of direct current of constant potentialfor supplying electrical potential to both of said tubes through theirrespective resistances,

coupling means for withdrawing substantieily sinusoidal oscillationsfrom the portion of said circuit in which said condenser is connected.

in oscillation generator, the combination comprising a condenser, aresistance connected across said condenser to form a circuit of nredeermined constant therewith, a pair of lotr-discharge tubes, each havingonly two one of their electrodes contwo plates of said condenser resincluding; a source of di -a potential applied to the glow-dischargetubes and "1g condenser in alternating a: rate determined by the timecon- OE said ircuit.

. on oscilietor of the character described, gaseous discherge tubeshaving only elec'rozies, 'or cpplyirr e, potentiei elect: ceus g sale;tubes conductive, occasioned b to tube for reducing: the eote.i-

tones to cause chargingtlel between the electrodes and extinguishing theconductivity of the other so that said tubes are alternately conductive,and means for producing an output voltage proportional to the cur rentthrough one of said tubes.

22. In an oscillator of the character described, a pair of gaseousdischarge tubes having only two electrodes, means for applying a.potential difference between said electrodes for causing said tubes tobecome conductive, means occasioned by the breakdown of each tube forreducing said potential difference and extinguishing the conductivity ofthe other so that said tubes are alternately conductive, means foradjusting the relative periods 0!. conductivity of said tubes,

for producing an output voltage proportional the current through one ofsaid tubes.

23. In an oscillator of the character described, a pair of gaseousdischarge tubes having only two electrodes, means for applying apotential between said electrodes for causing said tubes to becomeconductive, and means occasioned by the breakdown of each tube forreducing the potentiel between the electrodes and extinguishing theconductivity oi the other so that said tubes are alternately conductive.

